This invention relates generally to the inflation of inflatable vehicle occupant restraint airbag cushions used in inflatable restraint systems. More specifically, the invention relates to devices, systems and methods used in the inflation of inflatable vehicle occupant restraint airbag cushions, particularly close proximity inflatable airbag cushions.
It is well known to protect a vehicle occupant by means of safety restraint systems which self-actuate from an undeployed to a deployed state without the need for intervention by the operator, i.e., xe2x80x9cpassive restraint systems.xe2x80x9d Such systems commonly contain or include an inflatable vehicle occupant restraint or element, such as in the form of a cushion or bag, commonly referred to as an xe2x80x9cairbag cushion.xe2x80x9d In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, such airbag cushions begin to be inflated, in a matter of no more than a few milliseconds, with gas supplied or produced by a device commonly referred to as an xe2x80x9cinflator.xe2x80x9d
In practice, such airbag cushions may desirably deploy into one or more locations within the vehicle between the occupant and certain parts of the vehicle interior, such as the doors, steering wheel, instrument panel or the like, to prevent or avoid the occupant from forcibly striking such parts of the vehicle interior. Various types or forms of such passive restraint assemblies have been developed or tailored to provide desired vehicle occupant protection based on either or both the position or placement of the occupant within the vehicle and the direction or nature of the vehicle collision. For example, driver and passenger inflatable restraint installations have found wide usage for providing protection to drivers and front seat passengers, respectively, in the event of head-on type of collision.
While customary or common forms or types of driver and passenger inflatable restraint installations are helpful and generally effective in providing protection to drivers and front seat passengers, respectively, in the event of head-on types of collisions, further inflatable restraint developments have been sought to provide improved or increased vehicle occupant protection. For example, various forms or types of inflatable airbag cushions have been designed or proposed for placement and inflation in close proximity to the vehicle occupant such as to provide increased vehicle occupant protection in the event of a vehicle collision or impact inflicted or imposed from a direction other than head-on, i.e., xe2x80x9cside impact.xe2x80x9d In addition, particular forms or types of close proximity airbag cushions have been developed or proposed for increased or improved protection of particular regions or areas of an occupant. For example, thorax side impact airbag cushions or combined head and thorax side impact airbag cushions can be provided or included to provide increased or improved protection to either or both the head or thorax of a vehicle occupant.
One particularly effective form of side impact inflatable restraint is the subject of Hxc3x85land et al., U.S. Pat. No. 5,788,270, issued Aug. 04, 1998, the disclosure of which patent is hereby incorporated by reference herein in its entirety and made a part hereof. Inflatable elements, such as disclosed in Hxc3x85land et al., U.S. Pat. No. 5,788,270, may desirably include an inflatable portion formed from two layers of fabric with the front layer and the back layer of the fabric woven together at selected points. In particular embodiments, such selected points are arranged in vertically extending columns and serve to divide the inflatable part into a plurality of vertical parallel chambers. The spaces between the selected points permit internal venting between adjacent chambers of the inflatable element. Particular such inflatable devices/elements, such as utilized in applications to provide protection over an extended area and having a generally planar form, are frequently referred to as xe2x80x9cinflatable curtains.xe2x80x9d
A one piece woven construction has been found to be a particularly effective method of forming such inflatable element airbag cushions. In particular, one piece woven constructions have been found to provide a relatively low cost method of constructing suitable such airbag cushions which provide desired stand-up times. While inflatable element airbag cushions can, as is known in the art, be fabricated of various materials, nylon 6,6 has been found to be a particularly effective and useful material for use in the making or manufacture of inflatable curtain elements such as described above and having a one piece woven design.
Particular forms of close proximity inflatable airbag cushions for use in vehicular inflatable restraint systems include curtain and/or other side impact (head, thorax, combined, etc.) airbag cushions, knee airbag cushions bags as well as other relatively thin airbag cushions such as for near deployment to a vehicle occupant.
Upon deployment, the period of time during which an airbag cushion remains pressurized is commonly referred to as xe2x80x9cstand-up time.xe2x80x9d In practice, driver side and passenger side airbag cushions are typically desirably designed to begin deflating almost instantaneously upon deployment such as to avoid presenting an undesirably hard or ungiving surface to an oppositely seated vehicle occupant. However, in the event of certain accidents or collisions, airbag cushions which provide substantially longer stand-up times may be required or desired in order to provide a suitable desired level of occupant protection.
For example, one particularly troublesome form of side impact is commonly referred to as a xe2x80x9croll-over.xe2x80x9d In a roll-over incident, a vehicle may undergo a partial, complete or multiple roll-over. As will be appreciated by those skilled in the art, roll-over accidents can be particularly demanding on inflatable restraint systems. In particular, an airbag cushion designed to provide occupant protection in the event of a vehicle roll-over may be required or desired to remain pressurized for an extended or prolonged period of time, as compared to usual or typical driver side and passenger side airbag installations. For example, a roll-over protection side impact airbag cushion desirably remains pressurized or provides a stand-up time as long as about 5 seconds or more, such as evaluated based on a cushion internal pressure of greater than 25 kPa.
Further, as close proximity airbag cushions are designed and/or situated for near deployment to a vehicle occupant, such airbag cushions are generally required to be deployed into proper position within the vehicle interior in a very rapid manner, e.g., in less than 20 milliseconds. Further, proper or desired airbag cushion inflation commonly requires cushion pressures in excess of about 80 kPa at a point in time of 30 milliseconds after deployment initiation.
Additional system performance criteria include cushion in-position and integrity requirements as well as the need and desire to reduce, minimize or avoid damage to the cushion such as by reducing the molar flow rate and temperature of the inflation medium flowing into the cushion.
Further, satisfaction of such performance criteria at a lower or reduced cost and in a manner in which the envelope and weight of the system is minimized are ongoing design and engineering objectives. As will be appreciated, significant contributors to the cost of such inflation systems typically include cushion coating, inflator size, pyrotechnic requirements and the need for gas guides or other added design features. For example, cushion coating may be required or desired in order to avoid or minimize cushion stress and damage associated with deployment and inflation. By reducing the size of the inflator, e.g., minimizing the amount of required metal, and the amount or requirement for inclusion of a pyrotechnic, system costs can be reduced.
In view of the above, there is a need and a demand for improved apparatus or device for inflating such airbag cushions as well as for an improved corresponding inflatable restraint system and method for inflating a close proximity inflatable airbag cushion.
A general object of the invention is to provide one or more of an improved apparatus or device for inflating an inflatable device, an improved inflatable restraint system and an improved method for inflating a close proximity inflatable airbag cushion.
A more specific objective of the invention is to overcome one or more of the problems described above.
The general object of the invention can be attained, at least in part, through an apparatus for inflating an inflatable device. In accordance with one preferred embodiment of the invention, such an apparatus includes a chamber containing a gas mixture under an elevated pressure and having an average molecular weight of at least 10 and no more than 15. The gas mixture is effective to provide a gaseous inflation medium to inflate the inflatable device. The apparatus also includes a chamber opener actuatable to open the chamber. The apparatus further includes a diffuser assembly including at least one exit port for directing gaseous inflation medium from the apparatus to the inflatable device.
The prior art generally fails to provide inflator devices, inflatable restraint systems and methods for inflating a close proximity inflatable airbag cushion which satisfy various performance criteria such as relating to initial cushion inflation and stand-up in a manner in which the envelope and weight of the system is minimized and in which the costs have been reduced or minimized to as great an extent as may generally be desired.
The invention further comprehends an inflatable restraint system which includes at least one close proximity inflatable restraint device and an inflator effective, upon actuation, to provide a gaseous inflation medium to at least one close proximity inflatable restraint device. The inflator contains a gas mixture under an elevated pressure and having an average molecular weight of at least 10 and no more than 15. In accordance with one preferred embodiment of the invention, the gas mixture consists essentially of at least two members of the group consisting of helium, argon, carbon dioxide, nitrous oxide, nitrogen and oxygen.
The invention still further comprehends a method for inflating a close proximity inflatable airbag cushion. In accordance with one preferred embodiment of the invention, such method involves actuating an inflator device having a chamber containing a gas mixture under an elevated pressure with the mixture having an average molecular weight of at least 10 and no more than 15 and consisting essentially of at least two members of the group consisting of helium, argon, carbon dioxide, nitrous oxide, nitrogen and oxygen, the gas mixture effective to provide a gaseous inflation medium to inflate the close proximity inflatable airbag cushion.
As used herein, references to xe2x80x9cclose proximity airbag cushionxe2x80x9d are to be understood to refer to those airbag cushions such as curtain and/or other side impact (head, thorax, combined, etc.) airbag cushions, knee airbag cushions as well as other relatively thin airbag cushions which are designed and/or situated for near deployment to a vehicle occupant.
Further, references to xe2x80x9cside impactxe2x80x9d inflatable restraint systems, assemblies and the like are to be understood to generally encompass such systems, assemblies and such as adapted to provide vehicle occupant protection in the event of a side impact such as by providing one or more of roll-over protection (such as via an inflatable curtain inflation device), head/thorax protection (such as via a head/thorax side impact inflation device) and thorax protection (such as via a thorax side impact inflation device).
As used herein, references to xe2x80x9cdissociation,xe2x80x9d xe2x80x9cdissociation reactionsxe2x80x9d and the like are to be understood to refer to the dissociation, splitting, decomposition or fragmentation of a single molecular species into two or more entities.
xe2x80x9cThermal dissociationxe2x80x9d is a dissociation controlled primarily by temperature. It will be appreciated that while pressure may, in a complex manner, also influence a thermal dissociation such as perhaps by changing the threshold temperature required for the dissociation reaction to initiate or, for example, at a higher operating pressure change the energy which may be required for the dissociation reaction to be completed, such dissociation reactions remain primarily temperature controlled.
An xe2x80x9cexothermic thermal dissociationxe2x80x9d is a thermal dissociation which liberates heat.
Unless otherwise specifically identified, references herein to molecular weights are to be understood as being n reference to or in units of grams per mole.
Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings.